The use of ventilators and breathing circuits to assist in patient breathing is well known in the art. The ventilator and breathing circuit provide mechanical assistance to patients who are having difficulty breathing on their own. During surgery and other medical procedures, the patient is often connected to a ventilator to provide respiratory gases to the patient. One disadvantage of the use of such breathing circuits is that the air that is delivered to the patient's lungs does not provide the appropriate humidity to the lungs. In addition, the air that is delivered from a breathing circuit to the patient's lungs is not at the appropriate temperature.
In order to provide for proper humidity and temperature of the air, the use of an HME unit in the breathing circuit is used. Such HME units generally consist of a housing that contains a layer of flexible, fibrous, gas-permeable media or material. This media has the capacity to retain moisture and heat from the air that is exhaled from the patient's lungs and then transfer the captured moisture and heat to the inhaled air when the patient is inhaling. This fibrous material or media in the HME unit may be made of foam or paper or other suitable materials that are untreated or treated with hygroscopic material.
While the use of such HME units has addressed the problem of the heat and humidity of the air being provided to the patient in a breathing circuit, use of the HME unit has its own drawbacks. When administering medicine to a patient by use of a nebulizer or other treatment device, the fibrous media in the heat and moisture exchange unit can become clogged with the droplets of liquid medication that are provided from the nebulizer. Thus, to deliver medication via the nebulizer or other treatment device when a breathing circuit is in use, the HME unit must be removed from the circuit or from the nebulized air flow. Removal of the HME unit from the circuit takes the time of a health care provider that is better spent administering to the patient and opens the breathing circuit to the ambient air with possible contaminants.
It is highly desirable when using a breathing circuit to maintain the breathing circuit as a closed system. This is desirable because maintaining a closed system minimizes the exposure of the patient to bacteria and other contaminants, thus reducing the risk of the patient becoming infected. However, if nebulized medicine is to be administered to a patient in a breathing circuit with an HME unit and the HME unit is removed, the closed breathing circuit is breached and the breathing circuit is exposed to ambient air. This not only increases the risk of infection but also leaves the patient with a depressurized breathing circuit during the time that the closed breathing circuit is breached.
U.S. Pat. No. 6,095,135 (Clawson et al.) discloses a fairly complicated apparatus for heating and humidifying respiratory gases with a fitting joined to both a housing and tracheal tube device as well as a fitting closure assembly that moves to open and close a second end opening of the fitting. This patent discloses a bypass line or tube that is external to and outside of the HME portion of the apparatus. A nebulizer or other treatment device can be connected to this external bypass line. The fitting closure assembly is a valve that moves to direct air flow through the external bypass line so that the air does not pass through the housing of the HME unit. Some of the drawbacks of this invention are that it requires multiple components, including valves, fittings and a separate external bypass line outside of the housing of the HME unit in order to operate.
It is desirable to have an HME unit with self-contained internal bypass that will allow medicated air from a nebulizer to flow through the housing of the HME unit, but flow past the fibrous material in the HME unit and to the patient without requiring complicated valves and external bypass tubes. It is also desirable to have an HME unit for a breathing circuit that allows for medication to be delivered to the patient via a nebulizer without unduly consuming the time of the health care provider while maintaining the closed system of the breathing circuit.
The present invention meets these needs. The present invention provides an HME unit having a housing including a fibrous media and an internal bypass in the housing that enables air to flow past the fibrous media when desired (e.g., when using a nebulizer to provide medication to a patient). The present invention also provides a breathing circuit that includes an HME unit, a medication treatment device such as a nebulizer, and a ventilator. The respirator, the medication treatment device and the HME unit are connected in a closed system.
Various objects and advantages of the present invention will become apparent from the following detailed description when viewed in conjunction with the accompanying drawings, which set forth certain embodiments of the invention.